Method of shaping leather materials



Oct. 29, 1968 J. G. BUTLIN METHOD OF SHAPING LEATHER MATERIALS Filed April 26, 1966 \COPIPONENT BEING WETTED BY AlRLEss SPRAY COMPONENT DISTENDED 0N HEATED LAST HEATED LAST INVENTOR. L/0/7/7 Graham Bu '2 t 4 TTOENE Y5 United States Patent 3,407,421 METHOD OF SHAPING LEATHER MATERIALS John Graham Butlin, 110 Dunkirk Ave., Desborough, Northamptonshire, England Filed Apr. 26, 1966, Ser. No. 545,235 5 Claims. (Cl. 12142) ABSTRACT OF THE DISCLOSURE In the shaping of blanks of leather material, particularly shoe upper components, a predetermined amount of moisture is applied to one side of the blank and the blank then stretched around a heated last with the moistened surface in contact with the last. The added moisture is driven into the blank under the influence of the tempera ture gradient existing across the blank, while the blank is in stretched state, and escapes from the free surface of the blank.

This invention relates to the shaping of leather materials, for example, the shaping of upper parts in the course of manufacturing footwear.

It is well known that ordinary leather, that is leather of natural origin, becomes more distensible and the grain less liable to crack, if the leather is moistened and particularly if it is moistened and heated. It is a traditional practice in the manufacture of footwear, to moisten or mull the leather and particularly the upper material as a preliminary step to lasting, to facilitate the lasting operation and minimise the incidence of damage to the leather. The moisture added during mulling is of course additional to that already contained in the leather. After the lasting operation, which is not started until after the mulling has finished, the upper is left on the last for an extended time so that it will dry on the last and so better retain its shape. In modern practice the drying process is accelerated by the use of heat. By combining eflicient hot mulling techniques before the leather is shaped with rapid drying after shaping is completed it is possible to set the shape in the leather in a total process time of about -15 minutes. This produces a shoe that is as well shaped as onethat has been allowed to remain on the last for several days without the mulling or drying processes.

It has now been discovered that the leather can be shaped whilst moisture and heat are being applied thereto, the heating being continued with the leather held in position until the initially applied moisture has largely been driven away. In this way, mulling, shaping and setting can be accomplished in a single rapid operation of about 10 seconds duration giving a shape retention equivalent to several days on the last.

The invention in its broadest sense thus provides a process of shaping leather material in which a predetermined amount of moisture is applied to one surface of the leather and the leather material is deformed over a heated mould with the moistened surface in contact with the mould until the predetermined amount has been driven into the leather material, moisture being free to escape from the opposite surface of the leather material. As will be appreciated, the heated mould sets up a temperature gradient across the leather material. The moisture may be applied for a restricted time, and the leather material maintained at an elevated temperature until moisture equivalent in amount to the applied moisture has largely been lost through the free surface of the leather material. It is essential that the mould be in contact with the moistened surface of the leather material, in order that the positive driving-in of the moisture under the influence of the heat contained in the mould can be achieved.

In one convenient arrangement, the leather material is moistened over one surface, which may be achieved by spraying or otherwise applying liquid water (warm water may conveniently be used) and then is immediately stretched over a heated mould or former with the wetted surface next to the mould. Thus the leather material is deformed over the heated mould subsequent to the application of the moisture to the leather material surface.

Alternatively, the surface of the heated mould or former may itself be furnished with a source of moisture; for example it may be lined with a sheet of absorbent material containing moisture, or it may itself comprise for example sintered metal through which water or steam may be passed. Another possibility is for the former to be perforated so as to allow the passage of moisture. Where the mould or former is lined with a sheet of absorbent material, a predetermined amount of moisture, namely that contained in said material, is applied to the leather material and the latter can be held in contact with the heated mould for long enough to allow the bulk of this moisture to escape through the leather material. Where, on the other hand, the mould or former is itself permeable and moisture is applied from within it, means may be used to control the duration of the application of the moisture. For example, the mould may in effect rep resent a steam box and steam may be shut off after a predetermined time the leather material being kept in contact with the heated mould for long enough after this to allow it to dry off.

Another variant is to introduce the moisture by means of moisture-bearing pad or gauze which is pressed onto one surface of the leather material by a mould in the form of a hot block of metal or other substance with suitably high thermal conductivity.

It will be appreciated that the method of the present invention is applicable directly to the lasting of uppers, the last itself representing the mould or former. The last may for example be furnished with an absorbent liner over the area to be contacted by the upper or selectively at predetermined areas (the vamp areas for example car ry this layer, to leave the quarters relatively tight) the last itself being heated. The absorbent area will then be sprayed with water immediately before lasting and the heat retained in the last will be sufiicient to drive out the entrapped water. However, the method is of much wider application and is of especial use in pre-shaping uppers or upper parts such as the vamp.

From the foregoing, it will be appreciated that, in the majority of cases, the leather material will be wetted on the flesh side and the moisture driven out through the grain side.

For normal full chrome or combination tanned leathers with a shrinkage temperature above 90 C., and for the synthetic leathers so far tested, the quantity of moisture to be applied will normally be in the range from 315% by weight of the leather material, preferably around 5%. With a mould temperature of 100-1 C. it will then be found that a dwell time on the mould for the deformed leather of 5-15 seconds is suitable, preferably around 10 seconds for a mould temperature of 150 C.

For vegetable and combination tanned leather with a shrinkage temperature below C. the quantity of moisture to be applied will normally be in the range 25% by weight of the leather material, preferably around 3% with a mould temperature between 80 and 110 C., preferably C.

In the accompanying drawings, FIGS. 1 and 2 illustrate schematically suitable apparatus whereby the process described in Example I can be carried out.

As shown in FIG. 1, a leather vamp 1 is wetted on the flesh side 2 by moisture 4 discharged by airless spray wetter 5. The grain side 3 of the leather is not wetted.

EXAMPLE I An upper component (a vamp) was cut out of a full chrome side leather and moistened on the flesh side with 5% water applied by means of an airless spray wetter. It was then immediately stretched over a heated last, at 150 C. before the applied moisture had penetrated to any significant extent into the interior of the leather, for a period of seconds, the whole of the grain side of the leather apart from the gripped margins being exposed to the atmosphere.

Upon removal from the salt it was found that the shaped upper possessed an excellent degree of shape retention, the heating period having been sufficiently long to enable moisture equivalent in amount to the major part of the applied moisture to be driven through the leather and evaporated away from the grain surface, and the leather heat-set.

In this example, the last was heated by electrical cartridge heaters.

While the process of the present invention is of primary importance with ordinary leather, that is leather of natural origin, it can also be usefully applied to synthetic leathers, in particular the poromeric material now being sold under the Trademark Corfam.

The quantitative figures mentioned above as regards the applied moisture percentages, mould temperatures and dwell times are applicable similarly in the case of such synthetic materials. The following example illustrates the application of the present process to a Corfam" upper.

EXAMPLE II An upper shape of Corfam, thickness approx 0.05 in. was treated in exactly the same manner as the leather upper shape was treated in Example I above.

It was found again upon removal from the last that the shaped upper possessed an acceptable degree of shape retention although slightly inferior to that given by natural leather.

The term leather material is accordingly employed in the present specification and claims to denote both natural leather and those synthetic leather-like materials that can be shaped to an acceptable extent by the process.

Such synthetics generally comprise suitable textile or non-woven fabrics coated or impregnated with plastics or resins and grained to simulate the appearance of leather. Suitable coating materials are some polyurethanes and polyvinyl chlorides, sometimes with a top finish coat of cellulose nitrate, butyl methacrylate polymer emulsions, methyl vinyl ether-maleic anhy ride interpolymers, and the like.

I claim:

1. A process of shaping a blank leather material which comprises the steps of applying from about 2% to about 15% by weight of moisture to one surface of the blank, deforming the blank over a mould heated to a temperature of from about C. to about 180 C., the moistened surface of the leather being in contact with the mould and the opposite surface of the leather being open to the free escape of moisture from within, and maintaining the blank in contact with the heated mould for from about 5 to about 15 seconds to drive the applied moisture through the leather material and cause a substantially equal amount of moisture to escape from the opposite surface thereof.

2. A process according to claim 1 wherein the leather material is selected from the group consisting of normal full chrome leathers and combination tanned leathers with a shrinkage temperature above C., and synthetic leather-like materials, 3-15 by weight of moisture is applied to the leather material, the mould temperature is -180 C. and the dwell time of the deformed leather material on the heated mould is 5-15 seconds.

3. A process according to claim 2 wherein about 5% by weight of moisture is applied to the leather material, the mould temperature is about C. and the dwell time of the deformed leather material on the heated mould is about 10 seconds.

4. A process according to claim 1 wherein the leather material is selected from the group consisting of vegetable tanned leathers and combination tanned leathers with a shrinkage temperature below 90 C., 2-5% by weight of moisture is applied to the leather material, and the mould temperature is 80-110 C.

5. A process according to claim 4 wherein about 3% by weight of moisture is applied to the leather material, and the mould temperature is about 100 C.

References Cited UNITED STATES PATENTS 3,176,333 4/1965 Maeser 12-142 3.237227 1/1966 Bromfield 12-142 3,315,289 4/1967 Dew 12-146 PATRICK D. LAWSON, Primary Examiner. 

